title: Vertically-integrated multimode interferometer coupler for 3D photonic circuits in SOI.
abstract: Vertical optical coupling is demonstrated in a multimode interferometer structure fabricated using silicon-on-insulator (SOI) material. These CMOS-compatible couplers are suitable to be used to transfer optical power between stacked waveguide layers of a three-dimensional photonic circuit. Coupling between these layers can be restricted to certain regions by selectively fabricating a silicon channel between them, resulting in an isolated multimode waveguide section. Standard photolithography and etching techniques were used to fabricate proof-of-concept devices consisting of a channel waveguide coupling into a silicon waveguide that is vertically multimode. An optical coupling ratio of 93±4% between the upper and lower waveguide regions of the device was achieved with a coupler length of 241 µm.
authors.affiliation: Centre for Emerging Device Technologies, McMaster University, Department of Engineering Physics, 1280 Main Street West, Hamilton, ON, L8S 4L7, Canada.
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Brooks
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Knights
authors.forename: Paul E
authors.initials: PE
authors.lastname: Jessop